When I walk through St James’s Park, as I sometimes do, I am always (and it is always) struck by the number of people smiling at Grey Squirrels, photographing Grey Squirrels and feeding Grey Squirrels. These people, many of whom are ‘foreign’, from their accents at least, would be shocked to hear this lovely, friendly, cute mammal called a ‘tree rat’ (although they probably would say that there is not that much wrong with rats either).
But there is little or no doubt that the spread of the Grey Squirrel has pushed our native Red Squirrel back into the celtic fringe of the UK through a combination of disease transmission and competition. And so, cute as they are, I look somewhat askance at Grey Squirrels as I pass by them, although you can’t help but smile at them, can you?
It was, of course, the land owning class which introduced this cute but controversial mammal into our shores, and it is now the descendants 0f those landowners, and some foresters, who moan most about their continued existence in this country. There are various slightly crack-brained schemes around which are supposed to help Red Squirrels, and some that probably will, but there is now an approach that seems to offer more hope than the ‘get your gun out’ approach does.
Grey Squirrels were introduced into the UK from North America in the nineteenth century long after the main predator of squirrels had been extirpated from much of the UK. That species, was, and is, the Pine Marten. Perhaps, just perhaps, the Grey Squirrel has done so well because it has arrived in a predator-free zone?
There is now some evidence for this idea, quite good evidence which has been around for a while, although I missed it a couple of years ago (I suspect because I was working hard for WWF at the time). In the couple of days I spent with Forest Enterprise staff a couple of weeks ago, I sat through a presentation by Emma Sheehy. Her study in Ireland, where Grey Squirrels arrived only relatively recently but then romped westwards across the country reprising their impact on the Red Squirrel in Ireland as they had in Britain, showed that the increase in numbers and range of the Pine Marten seemed to be pushing Grey Squirrels back towards the Irish Sea and allowing Red Squirrels to regain their range too.
Pine Martens eat squirrels, red ones and grey ones, although of course, Red Squirrels evolved in a world full of Pine Martens whereas Grey Squirrels did not. In fact, interestingly (very interestingly), Grey Squirrels do not overlap in range with the marten species that might eat them in North America.
Grey Squirrels are bigger than Reds and therefore cannot escape Pine Marten attacks by seeking out the smallest branches of trees, and Greys spend more time on the ground than Reds and so are more vulnerable, perhaps, to Marten attacks.
The working hypothesis would be that if our landowners had not got rid of the Pine Marten then perhaps when they released the Grey Squirrel, it would not have been able to take such a hold on our woodlands (at the expense of our native Red Squirrel). And therefore, the interesting proposition is that if you have a box full of Pine Martens and let them go in your local wood they might well get rid of the Greys by eating a few of them and creating a ‘landscape of fear’ which rather cramps the style of the rest of them. Very interesting.
Now I am not suggesting that you should get a box full of Pine Martens and start letting them go, but I can see why Forest Enterprise should be interested in this idea. Of course, if we had a Forest and Wildlife Service then it would be a done deal! All those publicly-owned forests and a remit that requires the body to enhance biodiversity, and it would be a no-brainer (after careful consideration and trials etc etc etc).
I suspect that the main objections to there being more Pine Martens will come from shooting estates worried about their (non-native, introduced) Pheasants. Can you imagine the conflicting feelings of the members of the Country Land and Business Association over whether they could have an easy cost-effective solution to the problems that Grey Squirrels cause forestry but only at the expense of a native predator being re-established in our artificial countryside? I think we should give it a go. It all sounds great fun and rather promising, and an interesting case study for the role of native predators in preventing non-native species becoming established.
I’d be a bit surprised if I ever see Red Squirrels being admired by tourists in St James’s Park as it is more difficult to imagine Pine Martens getting to grips with Greys in the middle of our largest cities, but, you never know!
And I suspect those Lynx will sort out a few of the Muntjac too.
Emma Sheehy is now studying these issues at the University of Aberdeen. She is appearing on Radio 4’s Costing the Earth this afternoon at 330pm. Other press coverage here, here and an article by Emma here. And a bit of her science here.